In North America, severe whirlwinds, such as hurricanes, occur frequently, especially in the hot-weather season. Hurricanes are extremely destructive. The extreme differences in air pressure in the area of influence of a hurricane can remove entire roofs from buildings and wreak severe damage in other ways to and in buildings. There is an extremely high risk of injury to people from objects or components falling over or swirling around in the air.
In states adjoining the Gulf of Mexico, such as Florida, and on the Atlantic coast, residential buildings are often built without a cellar because the ground water level is very high. The buildings have only a concrete floor slab, which stands on concrete strip foundations. Generally, the walls of these houses are made from hollow masonry blocks. The roof structure comprises a wooden structure. Very often use is made of wooden trusses, especially nailed trusses, which span the entire interior of the building concerned. Such buildings, which are very economical to construct, cannot withstand the effects of a hurricane. The roof structure of these houses at the very least is often completely destroyed by a hurricane. When a hurricane approaches, the people in the residential areas affected are evacuated for their own safety.